Art of controlling sputtering and metal evaporation by means of a plane acceptor



Sept. 26, 1967 N. LAEGREID ETAL 3,344,054

ART OF CONTROLLING SPUTTERING AND METAL EVAPORATION BY MEANS OF A PLANE ACCEPTOR Filed March 2,. 1964 FIE. 1

T0 I r/l Paws? SUPPIY 7'0 POWER so y 27 FIEZE V 14 rraave rs United States Patent G F ART OF CONTROLLING SPUTTERING AND METAL EVAPORATION BY MEANS OF A PLANE ACCEPTOR Nils Laegreid, Minneapolis, Minn., and Roger M. Moseson, Rochester, N.Y., assignors to G. T. Schjeldahl Company, a corporation of Minnesota Filed Mar. 2, 1964, Ser. No. 352,417 2 Claims. (Cl. 204-298) The present invention relates generally to a material deposition system, and more particularly to a film deposition system wherein a material is being deposited on a Substrate member and wherein the crystalline and other physical properties of the deposited material may be carefully controlled.

In deposition systems generally, particularly those in which a gaseous medium is employed and a material is either deposited by sputtering techniques, ionic boinbardment techniques or thermal evaporation techniques; the system will employ a material source, a substrate upOn which the material is being deposited, and means for providing sufficient energy to the ions causing the transformation of source material into the gaseous phase and ultimately be deposited on the surface of the substrate. In most of these techniques, it is generally difficult, if not impossible, to carefully control the crystalline nature of the deposit. In this connection, substantial efforts have been made in the past to control the deposit by means of substrate heating and the like, however it is frequently found that the deposit will accept, or otherwise take the crystalline orientation of the substrate surface, and establish growth from that point forward. Accordingly, it becomes extremely difiicult to control the various electrical, magnetic, and other parameters of the deposit inasmuch as these parameters are normally dependent upon a certain crystalline orientation in the deposit. For example, polycrystalline material may be formed, or crystalline anomalies may result in the deposited product. In certain desposition techniques, it has been found possible to establish certain desired crystalline characteristics, and these may be achieved if proper deposition rates and other deposition parameters are extremely carefully controlled. However, if the deposition rate is increased, or if other conditions are changed, it frequently occurs that polycrystalline material will result, or other anomalies will be encountered in the finished product. In accordance with the present invention, deposition rates may proceed at a high level, and the material being deposited may be thermally treated during the dep osition process, and the characteristics of the deposit are found to be more predictable, controllable, and otherwise superior to those deposits obtained by conventional deposition techniques.

Briefly, in accordance with the present invention, a deposition system is established wherein a source of material to bedeposited is initially established, a substrate is providedfor receiving the material, and a source of energy is available in order to remove the material from the source and transfer it to the surface of the substrate. Treating means are available adjacent the substrate to heat incremental areas of the substrate to a temperature which is significantly greater than that of the remainder of the substrate, means being provided for moving the heater across a substantial extent of the substrate to treat other incremental areas in serial fashion. In addition, the material being deposited may be controllably deposited through a slit, or other aperture in a movable mask or the like which is moved across the surface of the substrate. The mask may be synchronized with the movement of the heater, if desired. While the technique of the present invention is most specifically adaptable to use with a system wherein the material being deposited is sputtered from the source surface, it will be appreciated that the invention has utility in connection with ionic bombardment, thermal evaporation, and other techniques wherein the material being deposited is caused to traverse a gaseous or evacuated medium between the source and the substrate surface. In addition, crystalline orientation may be established, controlled, and otherwise manifested by placing a seed crystal at one incremental area of the substrate, and establishing a quasi-molten zone adjacent to the area of the seed crystal, and thereafter causing the molten zone to migrate across the surface of the deposit. It has been indicated that the temperature of the incremental area being treated is significantly greater than that of the remainder of the substrate. It will be appreciated that this term refers to a temperature level which is achieved whereby the material being treated loses its memory of prior crystalline orientation, magnetic parameters, or other specific characteristics being controlled or studied. In this connection, the temperature difference between the treated zone and the remainder of the substrate may be only slight, however, it will be appreciated that this slight difference is suflicient to cause the treated zone to have a significant change insofar as crystalline memory, magnetic parameters, or the like are concerned. It will be appreciated, of course, that the substrate must be held at a temperature which, in general, is sufiicient to permit the evaporant, or other material suspended in the gaseous medium to condense unto the surface thereof.

Therefore, it is an object of the present invention to provide an improved technique for treating a thermally deposited material in a deposition system wherein the material deposited is exposed to a temperature level which is sufficiently high to establish a molten or quasi-molten zone, this zone being moved thereacross.

It is a further object of the present invention to provide an improved deposition system wherein incremental areas of a material being deposited are exposed to temperature levels which are significantly greater than that of the remainder of the substrate, the temperature level being sufiiciently high to create a significant change in the aclrystalline, magnetic, or other parameters of the materi It is yet a further object of the present invention to provide an improved deposition system wherein the substrate is exposed to the source material through a slit which moves across the substrate surface in a controlled fashion, the heater or other thermal treatment apparatus being moved in some chosen relationship with the slit or other aperture, as desired.

Other and further objects of the present invention will become apparent to those skilled in the art upon a study of the following specification, appended claims, and accompanying drawings wherein:

FIGURE 1 is a perspective diagrammatic view of a deposition system employing the technique of the present invention in conjunction therewith, the deposition system being utilized employing the well-known sputtering technique for providing the energy to remove the deposited material from its source and transfer the material to the substrate;

FIGURE 2 is a detail exploded perspective view, on a somewhat enlarged scale, of the substrate element of the deposition system shown in FIGURE 1, and illustrating the relationship of the heater to the substrate per se;

FIGURE 3 is a perspective view of the deposition control mechanism in the form of a moving aperture which is caused to traverse the surface of the substrate. in a periodic controllable manner, and illustrating, in phantom, the heater apparatus which is shown in detail in FIGURE 2; and

FIGURE 4 is an enlarged vertical sectional view taken as indicated from FIGURE 3.

In accordance with the preferred modification of the present invention, the deposition system generally designated includes a bell-jar 11 situated upon a working base plate 12. The bell-jar 11 and the surface 12 define an enclosure or cavity area 13 which provides the working area for the apparatus and technique of the present invention. The conduit 14 is in communication with the enclosure 13, and preferably is operatively associated with a vacuum pump or the like which is referred to by the character 15. The pump may be conveniently utilized to evacuate the enclosure 13, as indicated. A gas supply system is also utilized in connection with the bell-jar enclosure, the conduit 17 being in communication with the enclosure 13 through the base 12, and being in operative relationship with the gas resulating valve 18 for controlling the rate of flow of gas from a gas supply such as is designated at 19. Various inert gases may be utilized for either assisting in flushing the enclosure, or for actual use in connection therewith. For example, Argon gas is particularly desirable for use in an electrical sputtering or plasma deposition operation. For a general de scription of deposition techniques, such as those techniques which are commonly referred to as sputtering techniques today, reference is made to that certain article published in the Physical Review, vol. 102, No. 3, pp. 690-704.

The electron generating tube generally designated 21 is shown mounted in depending relationship from the base plate 12, the tube 21 also being in communication with the enclosure chamber 13. The tube 21 includes a thermal emission cathode or filament 22 which obtains electrical energy from the conductors 23 and 24, these conductors being operatively associated with a suitable power supply designated 27. Since the requirement of the power supply 27 is to provide current to heat the cathode, the voltage amplitude is not critical, and is determined by the actual requirements of the cathode filament 22. An additional conductor 28 is connected to the negative side of the power supply 27, such as along line 24, conductor 28 also being coupled to the negative side of a unidirectional power supply source 30. The positive side of the power supply 30 is coupled to an anode or plate 32 by means of the conductive support 29, the anode being fabricated from titanium or other suitable conductive material. A current limiting variable resistor 33 is utilized to control the supply to the anode 32. As indicated in the drawings, anode 32 is insulatively supported in the chamber 12 by a suitable insulator 26.

An electrode member 35 is disposed in. the plasma zone established within the chamber 13 between the cathode 22 and the anode 32, the electrodes 35 being supported on the base 12 by the bracket 34. Conductor 37 is coupled to the negative side of the unidirectional power source or supply 36, the magnitude of the energy being applied to the electrode 35 and between electrode 25 and anode 32 by the power supply 36 being controlled by the power supply and the current limiting variable resistor 38. Conductor 29a couples line 2) to the positive side of the power supply 36.

A substrate or workpiece 40 is disposed within the chamber 13 and is supported on the base plate 12 by means of the frame and mounting bracket 42. The subtrate 40 is designed for receiving a deposit such as a film deposit along the surface 40a. The substrate is interposed between a pair of frames 42 and 43. Frame 42 carries a slotted element 44 which is perforated as at 45 in order to receive evaporated atoms or the like therethrough, the slot providing the means by which the material may become impinged upon the surface of the substrate 40. The heated wire 47 moves in some chosen relationship, such as in synchronism with the slot 45 and will provide thermal energy to the substrate at a local area, which may be particularly at the point at which the deposit is being received. If desired, a seed crystal is interposed along the area 48 of the substrate 40 in order to control the crystalline orientation of the deposit and thereby form single crystals or the like as desired.

In order to move the slotted plate 44 across the surface of the substrate 40, a suitable drive means or the like such as the threaded shaft 53 is utilized. The threads of shaft 53 engage internally threaded sleeve 52. Sleeve 52 is secured to slotted plate 44, as at 51. Rotational energy may be provided to the shaft 53 by means of a magnetically coupled drive mechanism located partially externally of the bell-jar. The bar magnet 54 which is secured to the end of the shaft 53 is magnetically coupled to a matching magnetic element which is situated externally of the bell-jar enclosure.

The frame 43 carries a heated wire 47 which moves preferably in a chosen relationship such as in synchronism with the slot 45. The heated wire obtains its energy from an externally situated power supply such as the power supply 58, conductors 56 and 57 being utilized to carry the electrical energy to the heated wire.

EXAMPLE I A substrate is mounted between the slotted plate frame holder 42 and the heated wire retainer 43, the combination being supported along the surface of the base plate 12 by suitable brackets, as indicated in the drawings. The chamber is also provided with a source of evaporant by means of the target 35, the space between the target 35 and the substrate 40 being a plasma generation area which exists between the cathode 22 and the anode 32. The target was 83-17 Permalloy. The chamber is then evacuated down to a pressure of 10 Torr, and thereafter an argon atmosphere is introduced to a pressure of 10 Torr. As previously indicated, this gas is introduced to the chamber by means of the supply line 17. In this specific operation, the target or source 35 and the substrate 40 are spaced apart a distance of four inches, the slotted mask having an aperture of one-quarter inch being immediately adjacent the surface of the substrate 40.

The cathode 22 is then energized with the element being heated to a temperature which is suflicient to cause thermal emission of electrons therefrom. Simultaneously, the anode 32 is maintained at a positive potential in order to attract the flow of electrons from the cathode into the area of the anode. While the thermally emitted electrons flow toward the anode, and while they are passing through the gas which is present in the enclosure or chamber, collisions will occur with the atoms and molecules of the gas, and these collisions will remove electrons from the atoms and molecules and thereby form positively charged gas particles. A concentration of electrons and ions flowing between the cathode and the anode is accordingly developed. As the electrons move in this area, collisions occur with the argon gas which is present in an amount, as indicated, of 10" Torr. These collisions will dislodge an electron from the gas atomic or molecular structure, and cause the particles to become ionized and attracted to a properly energized target or source 35. The collisions which occur between the charged gas particles of substantial mass and the surface of the target 35 cause a dislodging of material from the surface of the target 35, these materials when being free to move toward the substrate 40, as a statistical quantity will do. This portion of the operation is, of course, a typical and conventional sputtering technique. In this operation, a potential of 45 volts was applied to the electrode 32 while a potential of minus 500 volts was applied to the surface of the source material or target 35. The substrate 40 was maintained at a floating potential. Accordingly, the gaseous plasma will be attracted to the negatively charged target 35, and the plasma will cause sputtering of surface atoms from the surface thereof. The growth rate under these conditions is about Angstroms per minute.

The slot has a width of about one-quarter inch, and permits the evaporant or sputtered atoms to move therethrough and onto the surface of the substrate 40. The heated wire which moves in some relationship moves in syncronism with the slot and is adapted to heat the local area of the substrate 40 to a temperature of about 300 C., which has been found to be above the temperature at which significant magnetic disorders occur in the material being deposited. In other words, it is at this temperature where significant changes begin to occur with the magnetic structure of the material. The deposited material will accordingly assume a crystalline structure which is oriented similarly to a seed area which is disposed adjacent the edge of the substrate 40a as indicated, such as at 55. The wire and slot move at a rate equivalent to provide one traverse across the surface of the glass substrate 40 during the deposition, starting at the seed area.

The resultant deposit is considered desirable from its uniform crystalline orientation, as well as from its magnetic properties. The control available by the sputtering technique is obviously desirable, and when the added control which is available in the deposit is clearly responsible for permitting additional parameters to be carefully controlled and monitored. Other materials including germanium, silicon and various metal oxides may be treated in this fashion.

It will be appreciated, of course, that the specific examples given herein are for purposes of illustration only and are not to be otherwise construed as a limitation upon the scope to which the present invention is entitled. Therefore, those skilled in the art may depart from these specific examples without actually departing from the spirit and scope of the present invention.

What is claimed is:

1. In a cathode sputtering apparatus including a cathode target comprising a source of material to be deposited, an anode means for providing an electrical bias potential between said anode and said cathode target, means for receiving a substrate having a deposition area for receiving said material disposed in spaced relationship from said source, and energy means for the sputtering removal of said material from said source and enabling the sputter removed material to migrate to said substrate, said means for receiving said substrate positioning said substrate in the line of sight of said target, means for providing the arrangement of a seed crystal on the surface of the said substrate at a first incremental area thereof, mask means disposed immediately adjacent said substrate and having a slot formed therein for periodically exposing a portion of said substrate surface including said first incremental area to said remote source, means for moving said masking means across the said deposition area, heating means coupled to said mask means for heating an incremental area of said substrate to a temperature significantly greater than that of the remainder of said substrate, said heating means being normally disposed along that certain area of said substrate exposed by said masking slot and being adapted to heat said certain area, and means for moving said heating means across said deposition area in syncronism with the slot formed in said masking means.

2. The deposition system as defined in claim 1 being particularly characterized in that said gaseous atmosphere is argon at a pressure of about 10- Torr.

References Cited UNITED STATES PATENTS 1,256,599 2/1918 Schoop.

2,160,981 6/1939 OBrien 118301 3,160,521 12/1964 Ziegler et a1 148--175 X 3,160,522 12/1964 Heywang et al. 148--174 X 3,206,322 9/ 1965 Morgan 117-4 JOHN H. MACK, Primary Exaaminer.

R. K. MIHALEK, Assistant Examiner. 

1. IN A CATHODE SPUTTERING APPARATUS INCLUDING A CATHODE TARGET COMPRISING A SOURCE OF MATERIAL TO BE DEPOSITED, AN ANODE MEANS FOR PROVIDING AN ELECTRICAL BIAS POTENTIAL BETWEEN SAID ANODE AND SAID CATHODE TARGET, MEANS FOR RECEIVING A SUBSTRATE HAVING A DEPOSITION AREA FOR RECEIVING SAID MATERIAL DISPOSED IN SPACED RELATIONSHIP FROM SAID SOURCE, AND ENERGY MEANS FOR THE SPUTTERING REMOVAL OF SAID MATERIAL FROM SAID SOURCE AND ENABLING THE SPUTTER REMOVED MATERIAL TO MIGRATE TO SAID SUBSTRATE, SAID MEANS FOR RECEIVING SAID SUBSTRATE POSITIONING SAID SUBSTRATE IN THE LINE OF SIGHT OF SAID TARGET, MEANS FOR PROVIDING THE ARRANGEMENT OF A SEED CRYSTAL ON THE SURFACE OF THE SAID SUBSTRATE AT A FIRST INCREMENTAL AREA THEREOF, MASK MEANS DISPOSED IMMEDIATELY ADJACENT SAID SUBSTRATE AND HAVING A SLOT FORMED THEREIN FOR PERIODICALLY EXPOSING A PORTION OF SAID SUBSTRATE SURFACE INCLUSING SAID FIRST INCREMENTAL AREA TO SAID REMOTE SOURCE, MEANS FOR MOVING SAID MASKING MEANS ACROSS THE SAID DDPOSITION AREA, HEATING 